1. Field of the Invention
The present invention relates to a method of manufacturing a nonaqueous electrolyte secondary battery.
2. Description of Related Art
A nonaqueous electrolyte secondary battery such as a lithium ion secondary battery (lithium secondary battery) has a lighter weight and higher energy density than existing batteries. Therefore, recently, a nonaqueous electrolyte secondary battery has been used as a so-called portable power supply for a PC, a portable device, or the like or as a drive power supply for a vehicle. In particular, it is expected that a light-weight lithium ion secondary battery capable of obtaining a high energy density will be increasingly widely used as a high-output power supply for driving a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), or a plug-in hybrid vehicle (PHV).
During the manufacturing of a nonaqueous electrolyte secondary battery, initial charging is performed as a finishing step after a battery construction step. Due to this initial charging, a film (so-called solid electrolyte interface (SEI)) is formed on a negative electrode. This film can allow smooth intercalation and deintercalation of ions, which are charge carriers, and functions as a passive film which suppresses the reductive decomposition of an electrolytic solution.
In a nonaqueous electrolyte secondary battery, it is important to form a good film by initial charging from the viewpoint of retaining the battery capacity. Japanese Patent Application Publication No. 2008-91259 (JP 2008-91259 A) discloses a configuration of initially charging a nonaqueous electrolyte secondary battery, which contains a nonaqueous electrolytic solution containing vinylene carbonate as a negative electrode film forming agent, in an environment of −5° C. to 10° C. at a current value of 1.0 C or lower such that a good film is formed on a negative electrode to improve the capacity retention of the nonaqueous electrolyte secondary battery.
However, as a result of thorough investigation, the present inventors found that the initial resistance of a nonaqueous electrolyte secondary battery may increase only with the configuration of forming a film on a negative electrode using a negative electrode film forming agent as disclosed in JP 2008-91259 A.